1. Field of the Invention
This invention relates to a gene encoding a proteinous component PZP-4 of porcine zona pellucida, and to a contraceptive vaccine antigen prepared by expressing the gene, for use in human or other animals.
2. Prior Art
Unlike the general sterilization such as Pill, IUD, condom, rhythm method, operative sterilization, etc., the sterilization by inoculation of vaccines belongs to an immunological one. It has been suggested that zona pellucida can be used as an antigen for the contraceptive vaccine. When the zona pellucida is therefore inoculated as a vaccine antigen into human or other animals, a specific antibody to the antigen is formed in their bodies, by which fertilization or ovum growth is inhibited to result in contraception.
Among zona pellucidae from various sources, porcine zona pellucida has been mainly studied as a source of such a vaccine antigen. Development of the contraceptive vaccines has been attempted using the whole porcine zona pellucida (PZP-1 of a molecular weight 80 to 90 kDa, PZP-2 of 60 to 65 kDa, PZP-3 of 55 kDa, and PZP-4 of 20 to 25 kDa (Wassarman P. M., "Zona Pellucida Glycoproteins", Ann. Rev. Biochem., 1988, Vol.57, pp.415-420)), or using only the PZP-3 component (Sacco A. G., "Zona Pellucida: Current Status as a Candidate Antigen for Contraceptive Vaccine Development", American Journal of Reproductive Immunology and Microbiology, 1987, Vol.15, pp.122-130).
Unfortunately, it is necessary to collect a large quantity of ovaries in order to obtain a sufficient amount of a PZP antigen to prepare a contraceptive vaccine, because a zona pellucida is present only in ovaries. This entails a problem in that an industrially sufficient amount of the antigen cannot be produced. In addition, during purification of zona pellucida other ovarian tissues may be contaminated in a preparation, resulting in an enhanced side effect in animals when the preparation was administered thereto as a vaccine.
It is therefore desirable to prepare a zona pellucida or its components by means of genetic engineering techniques, because a polypeptide useful for a contraceptive vaccine can be obtained in a large scale without depending on materials from living bodies.
An object of the present invention is to provide a genetic engineering process for the production of a zona pellucida PZP-4-related (poly)peptide useful for a contraceptive vaccine.
Another object of the present invention is to provide a contraceptive vaccine which can be prepared in a large scale from a supplier other than living bodies.